Generally, when a reactive gas is applied on the upper surface of a wafer, the temperature of which is increased, it is deposited thereon through a chemical reaction facilitated by heat. As such, in the case where the temperature of the wafer is not uniformly increased, part of the thin film is deposited on the wafer differently from the intended design specification, undesirably causing subsequently produced semi-conductor devices to be defective.
The heating temperature of a heater mounted in a conventional CVD apparatus varies depending on the production environment.
Therefore, the case where the heating temperature of the heater is not uniform causes variation in the amount of heat that is transferred to the wafer, whereby the wafer has a temperature different from that of the design specification, thus making it difficult to form a uniform deposition film.
That is, in the case where the heating temperature of the heater is different in portions thereof, the thin film may be deposited thickly over the area of the heater having a relatively high temperature, or may be deposited thinly over the area of the heater having a relatively low temperature, and thus the deposition film may be non-uniformly formed on the wafer.
FIGS. 1 and 2 are schematic views illustrating a conventional CVD apparatus for depositing a thin film on a wafer, and a high temperature area A and a low temperature area L of the heater.
As illustrated in the drawings, the conventional CVD apparatus includes a process chamber 100, in which the deposition of a thin film is carried out. In the process chamber 100, a shower head 102 for spraying a reactive gas and a heater 103 formed of ceramic or AlN, on which a wafer is placed, are mounted. Further, the conventional CVD apparatus has an inlet gas line 101 for supplying the reactive gas into the process chamber 100, a pumping line 104 for discharging the reactive gas after deposition, a heater supporting member 105 for supporting the heater 103, a bellows 106 for protecting the heater supporting member 105, and a thermal insulation reflecting plate 120.
In order to maintain the temperature of the surface of the heater on which the wafer is placed uniform, as illustrated in FIGS. 1 and 2, the conventional CVD apparatus is characterized in that the thermal insulation reflecting plate, in which a portion thereof, corresponding to the area of the heater having a heating temperature higher or lower than the remaining area of the heater, is open, is provided below the heater using holding pins.
However, the method of emitting reflected heat downward using the thermal insulation reflecting plate having the open area formed below the heater, as mentioned above, is limited in its ability to improve the uniformity of the heating temperature because heat transfer is realized only in the form of radiation via the open area of the thermal insulation reflecting plate below the heater.
As such, heat transfer may be performed in the form of conduction by direct contact or convection by gas, in addition to the radiation, and thus there is a need to implement such heat transfer methods so as to realize increased efficiency.